Sudden reduced fuel efficiency

[Wasted]

I realize there is a similar thread going but i think it's different enough for a new one..

When i bought the car i would get about 380 miles out of the 50l tank, after cleaning the SPI with carb cleaner, FULL service, fuel filter, tracking, tyres i was getting 420 miles out of a tank and it stayed in that range for a year. For the last couple of months it's dropped to 320 miles if i'm lucky. Noticed the drop just after i fitted a new end link to the passenger side anti-rolebar.

I cleaned the SPI again about 6 months later as it was covered in **** again, assuming unburnt fuel deposits.

There is a fist sized hole in the back box which i am led to believe won't account for a huge drop in mpg and the air filter could probably do with changing but i don't see these 2 problems causing this huge drop in efficiency.. I am not down on power that i have noticed, so i'm discounting HT, plugs and leads. I am welcome to be corrected

I'm looking for ideas and other places to look, thanks in advance for any help or advice.

 

[astranaut]

I noticed an mpg drop when my back/middle box went, before i used to get 70+ miles off a tenner, it dropped to about 50 with a ****ed exhaust so worth doing. When i fixed it i also noticed it responded a lot better and picked up much quicker.

 

[bigspj]

There is a fist sized hole in the back box which i am led to believe won't account for a huge drop in mpg and the air filter could probably do with changing but i don't see these 2 problems causing this huge drop in efficiency.. I am not down on power that i have noticed, so i'm discounting HT, plugs and leads. I am welcome to be corrected

I'm looking for ideas and other places to look, thanks in advance for any help or advice.

Hole in the backbox will seriously affect Mpg. A dirty air filter will not let air pass through so easily and as a result more fuel will get pulled in instead. Not being down on power is due to the hole in the backbox freeing the exhaust flow up, youll probably find it goes like bloody hell though. Get the backbox replaced or fixed and for the sake of a few quid stick a new air filter in. Dont carry any unwanted rubbish around in the car that will reduce fuel efficiency. Having a roof rack on and also driving with windows down will reduce mpg as the car is creating more drag. :-)

 

[Wasted]

Sweet thanks for that dude, i'll sort it. Might even go for one of those big bore exhausts, i've gotten used to the noise

Binned the roof rack and the tow bar as soon as i got it.